Incorporation of high molecular weight fluorocarbon polymer in arylene sulfide polymer

ABSTRACT

High molecular weight fluorocarbon polymer is incorporated into arylene sulfide polymer coating dispersions by (a) intensive milling of the fluorocarbon polymer and a liquid capable of wetting same and (b) thereafter adding the arylene sulfide polymer and a pigment of filler and subjecting the mixture to additional intensive milling.

United States Patent [191 [111 3,856,735 Blackwell Dec. 24, 1974INCORPORATION OF HIGH MOLECULAR [56] References Cited WEIGHTFLUOROCARBON POLYMER IN UNITED STATES PATENTS ARYLENE SULFIDE POLYMER3,622,376 11/1971 Tieszen et a1. 260/29.6 F [75] Inventor: Jennings P.Blackwell, Bartlesville,

Okla Primary Examiner-Harold D. Anderson [73] Assignee: PhillipsPetroleum Company,

Bartlesville, Okla. [57] ABSTRACT [22] Filed: Oct. 19, 1972 Highmolecular weight fluorocarbon polymer is incorporated into arylenesulfide polymer coating disper- [zu Appl' 299065 sions by (a) intensivemilling of the fluorocarbon polymer and a liquid capable of wetting sameand (b) [52] US. Cl.... 260/29.6 F, 117/132 B, 117/132 CF, thereafteradding the arylene sullficle polymer and a 260/29.6 NR, 260/33.4 F,260/900 pigment of filler and subjecting the mixture to addi- [51] Int.Cl. C08f 45/24 tional intensive milling. [58] Field of Search 260/29.6F, 900, 33.4 F

7 Claims, No Drawings INCORPORATION OF HIGH MOLECULAR WEIGHTFLUOROCARBON POLYMER IN ARYLENE- SULFIDE POLYMER BACKGROUND OF THEINVENTION This invention relates to the preparation of arylene sulfidepolymer coating compositions containing high molecular weightfluorocarbon polymer.

Arylene sulfide polymers are known for their desirable characteristicsas coating compositions as shown for instanceby Ray US. Pat. No.3,492,125. It has been found that in some instances it is preferred toincorporate a small amount of fluorocarbon polymer with the arylenesulfide polymer coating composition. While relatively low molecularweight fluorocarbon polymer such as that sold by LNP Corp. under thetrademark TL-126 can be incorporated into such dispersions relativelyeasily, it has been found that the high molecular weight fluorocarbonpolymers are difficult to disperse evenly in an arylene sulfide polymercoating composition.

BRIEF SUMMARY OF THE INVENTION It is an object of this invention toprovide an arylene sulfide polymer coating composition containing a highmolecular weight fluorocarbon polymer.

It is a further object of this invention to provide a method forincorporating high molecular weight fluorocarbon polymers into arylenesulfide polymer coating compositions.

It is yet a further object of this invention to provide a convenientmethod of determining the optimum cure for an arylene sulfide polymercoating composition.

And still yet a further object of this invention is to provide anarylene sulfide polymer coating having smooth surface characteristics.

In accordance with this invention, the high molecular weightfluorocarbon polymer is first subjected to intensive milling in a liquidcapable of wetting same and thereafter mixed with arylene sulfidepolymer and a pigment or filler, with the resulting mixture beingsubjected to additional intensive milling.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The instant invention isapplicable to the incorporation of any high molecular weightfluorocarbon polymer into arylene sulfide polymer coating compositions.The preferred fluorocarbon polymer is polytetrafluoroethylene. Theinvention makes possible the successful incorporation of fluorocarbonpolymers having a high molecular weight. By high molecular weight ismeant polymers of such molecular weight that no flow is obtained in theASTM D 1238 melt viscosity test at 380C using a 5,000 g weight. Probablysuch polymers have a number average molecular weight of greater thanmillion. These are the types of polymers gener ally referred to asextrusion or molding grade polymers. Such polymers are sold undertrademarks Teflon-5, Teflon-6, Teflon 7, and Halon 6-80. The preferredpolymers pass the F DA. specification for acceptable PTFE(polytetrafluoroethylene) in food service which requires a meltviscosity of at least 10,000 poise at 380C as determined by ASTM D 1238and a thermal instability index (T11) of less than 50 as determined byASTM The invention is applicable to the production of dispersions of anyarylene sulfide polymer although the preferredpolymer is polyphenylenesulfide having a melting or softening point of at least 300F, preferably400F to 850F.

The intensive milling used in the initial dispersion of the fluorocarbonin the liquid and the subsequent milling of this mixture with a pigmentand arylene sulfide polymer can be accomplished by the use of aconventional ball mill, a conventional rod mill, or a vibratory ballmill. The balls or rods can be made of steel, ceramic materials such asBurundum (a high-fired ceramic), and the like. Both of the operationscan be carried out in the same mill or separate mills, including the useof different types of mills for each of the two steps.

It is essential that there be some pigment or filler present during thesecond milling step. The ratio of fluorocarbon to pigment can vary from0.1 to 3 parts by weight of fluorocarbon polymer per 1 part by weight ofpigment or filler. Preferably about 0.5 to 2 parts of fluorocarbonpolymer per 1 part by weight of pigment or filler is utilized.

The pigment or filler can be any pigment or filler capable ofwithstanding a curing temperature of at least about 300F, preferably600-850F. It is preferred to use pigments and the most preferredpigments are titanium dioxide or black iron oxide. Particularly suitableare combinations of titanium dioxide and iron oxides. Other suitablepigments include red iron oxide, brown iron oxide, carbon black, andzinc oxide. Suitable fillers include such materials as silica and talc.

The liquid in which the fluorocarbon polymer is milled can be any liquidcapable of wetting the fluorocarbon. The preferred liquid is watercontaining a surface active agent. Other suitable liquids includeethylene glycol, propylene glycol, and mixtures of such liq uids withwater. Any conventional surface active agent can be utilized; however,nonionic surface active agents are preferred.

While the ratio of solids (comprising the arylene sulfide polymer,pigment, and fluorocarbon polymer) to liquid can vary depending on theparticular coating application, it is generally preferred to have adispersion of about 15 to 40 weight percent solids.

The initial intensive milling of the liquid and fluorocarbon polymer canbe carried out for a time of greater than about 4, preferably within therange of 8 to 96 hours with the milling time for the subsequentintensive milling of the pigment or filler and arylene sulfide polymerwith the liquid and fluorocarbon polymer being carried out for a time ofgreater than about 2, preferably within the range of4 to 48 hours, thistime generally being about one half the time required in the initialmilling. With a high speed vibrator such as the /ibra tom with stainlesssteel balls the first stage intensive milling can be accomplished in 0.5to 10 hours and the second stage of intensive milling can be carried outin 0.5 hour to 5 hours.

The ratio of arylene sulfide polymer to fluorocarbon polymer in thefinal cured coating composition will generally range from 2:1 to 40:1,preferably 4:1 to 15:1.

It is essential that the pigment, fluorocarbon polymer, and arylenesulfide polymer be in particulate form. In general, the smaller theparticle size the better the dispersion which can be produced. Asuitable particle size for the fluorocarbon polymer is 40 mesh or curedcoating. The microknife hardness was 250, and the coating had anadhesion rating of less than 4 (scale l-l5, l best, 4 considered verygood).

EXAMPLE [I Slurries were made by ball milling Teflon-5 with watercontaining 2 weight percent nonionic wetting agent,octylphenoxypolyethoxy ethanol (Triton X- 100, Rohm & Haas Co.) for 24hours before adding the other ingredients in ball milling for times asset out hereinbelow.

Composition Time for Ball-Milling: Reference (Parts/100 PPS) Teflon PPSPigment Total Example I 15 Fe O /l5 T-5* 24 I6 40 hr Run 2 l5 Fe O /7.5T-5 24 I6 40 Run 3 33 Fe /l T5 24 66 90 Run 4 33 Fe O 33 T-5 24 66 90Run 5 33 Ti l3 T-5 24 24 48 T-5 Teflon-5, molding grade P'TFE having aparticle size of about 325 microns and believed to be ofu molecularweight greater than 10,000,000. This polymer exhibited a 0 flow in theASTM D 1238 melt viscosity test at 380C using a 5.000 g. weight.

The final dispersion can be applied to a substrate by any conventionalmeans such as spraying, or with a doctor blade or the like. 1

The resulting coating can be cured, for instance by heating to atemperature of at least 500F, preferably 600-850F for at least 5minutes, preferably minutes to 2 hours. The coatings can be cured at thehigher temperatures with the shorter times. It is particularly desirablein many instances to utilize as the pigment a material which will changein color after a temperature treatment which corresponds to the point atwhich the polymer is properly cured. For instance black ferric oxideremains jet black after 15 minutes at 600F but is dull black afterminutes at 600F and is dull brown (or, depending on other ingredients, abrownish hue or a red or maroon clearly distinguishable from theoriginal black) after 60 minutes at 600F. This color change can bevisually observed and the coated article removed at just the right stageof cure. Also this allows a color difference when a second coat of thesame composition is applied so as to give a ready means of determiningif the second coat completely covers the surface.

EXAMPLE I A 9 gram sample of Teflon-5 powder was ball milled for 24hours with 300 ml of water containing 6 grams of a nonionic wettingagent sold under the trademark Triton X-l00. The Teflon-5polytetrafluoroethylene powder had an average particle size of 325microns before milling. To this aqueous slurry was then added 60 gramsof polyphenylene sulfide having an inherent viscosity of about 0.15 asdetermined by using 0.25 percent ofthe sample in chloronaphthalene at206C. This polyphenylene sulfide had a particle size of less than 60mesh. Also added to the aqueous slurry was 9 grams of black iron oxide.The resulting mixture was ball milled for 16 hours. This slurry wassprayed through a 100 mesh screen onto a 3 X 6 X 0.020 inch aluminumalloy coupon which had been degreased by washing in acetone and blastedwith No. 100 abrasive. The resulting coating was cured for 30 minutes at700 F to give a very smooth coating. The coating color changed fromblack in the uncured coating to a brownish hue in the All slurries weresprayed through mesh screen with a Binks Model 188 spray gun ontoaluminum coupons as in Example I and cured at 700F for 30 minutes. Inall instances a smooth coating was obtained so that the excess millingtime used in Runs 3 and 4 was not really required for this result.

CONTROL Similar dispersions to those of the Examples were made exceptthe polyphenylene sulfide, polytetrafluoroethylene, pigment, and aqueoussurface active agent solutions were all ball milled together for varioustimes up to 7 days. The resulting coatings in each case were rough. Anidentical procedure (all ingredients mixed together) utilizing lowmolecular weight fluoro carbon polymers such as TL-l26 which has a meltviscosity at 380C of 4 X 10'' gave a smooth coating.

While this invention has been described in detail for the purpose ofillustration it is not to be construed as limited thereby but isintended to cover all changes and modifications within the spirit andscope thereof.

I claim:

1. A process for forming poly(arylene sulfide) coating dispersionsconsisting essentially of the following steps: subjecting fluorocarbonpolymer, in particulate form having a molecular weight sufficient togive a melt viscosity flow of 0 at 380C using a 5,000 g. weight, tointensive milling by ball milling or rod milling with a liquid selectedfrom water, ethylene glycol or propylene glycol; and thereafter addingthereto said poly- (arylene sulfide) in particulate form and a pigmentor filler in particulate form and subjecting the resulting mixture toadditional intensive milling by ball milling or rod milling, the ratioof said fluorocarbon polymer to said pigment or filler being within therange of 0.1 to 3 parts by weight of fluorocarbon polymer per 1 part byweight of said pigment or filler, the ratio of said poly(arylenesulfide) to said fluorocarbon polymer being within the range of 2:l to40:1, and wherein the total solids content is within the range of IS to40 weight percent based on the total weight of said dispersion.

2. A method according to claim 1 wherein said fluorocarbon ispolytetrafluoroethylene.

3. A method according to claim 2 wherein said liquid is water containinga surface active agent.

7. A method according to claim 4 wherein said intensive milling of saidliquid and fluorocarbon polymer is done by ball or rod milling for atime period of greater than 4 hours and said intensive milling of theresulting mixture with said polyphenylene sulfide and said pigmentorfiller is done in a ball or rod mill for a time of

1. A PROCESS FOR FORMING POLY(ARYLENE SULFIDE) COATING DISPRSIONCONSISTING ESSENTIALLY OF THE FOLLOWING STEPS: SUBJECTING FLUOROCARBONPOLYMER, IN PARTICULATE FRM HAVING A MOLECULAR WEIGHT SUFFICIENT TO GIVEA MELT VISCOSITY FLOW OF 0 AT 380*C USING A 5,000 G. WEIGHT, TOINTENSIVE MILLING BY BALL MILLING OR ROD MILLING WITH A LIQUID SELECTEDFROM WATER, ETHYLENE GLYCOL OR PROPYLENE GLYCOL; AND THEREAFTER ADDINGTHERETO SAID POLY(ARYLENE SULFIDE) IN PARTICULATE FORM AND A PIGMENT ORFILLER IN PARTICULATE FORM AND SUBJECTING THE ESULTING MIXTURE TOADDITIONAL INTENSIVE MILLING BY BALL MILLING OR ROD MILLING, THE RATIOOF SSAID FLUOROCARBON POLYMER TO SAID PIGMENT OR FILLER BEING WITHIN THERANGE OF 0.1 TO 3 PARTS BY WEIGHT OF FLUOROCARBON POLYMER PER 1 PART BYWEIGHT OF SAID PIGMENT OF FILLER, THE RATION OF SAID POLY(ARYLENESULFIDE) TO SAID FLUOROCARBON POLYMER BEING WITHIN THE RANGE OF 2:1 TO40:1, AND WHEREIN THE TOTAL SOLIDS CONTENT IS WITHIN THE RANGE OF 15 TO40 WEIGHT PERCENT BASED ON THE TOTAL WEIGHT OF SAID DISPERSION.
 2. Amethod according to claim 1 wherein said fluorocarbon ispolytetrafluoroethylene.
 3. A method according to claim 2 wherein saidliquid is water containing a surface active agent.
 4. A method accordingto claim 3 wherein said poly(arylene sulfide) is polyphenylene sulfide.5. A method according to claim 4 wherein said pigment is selected fromthe group consisting of titanium dioxide, iron oxide, and mixturesthereof.
 6. A method according to claim 7 wherein said pigment,fluorocarbon polymer, and poly(arylene sulfide) particles each have aparticle size of less than 40 mesh.
 7. A method according to claim 4wherein said intensive milling of said liquid and fluorocarbon polymeris done by ball or rod milling for a time period of greater than 4 hoursand said intensive milling of the resulting mixture with saidpolyphenylene sulfide and said pigment or filler is done in a ball orrod mill for a time of greater than 2 hours.